Track and field is a sport in which athletes compete in running, jumping, and throwing. One of the throwing events is the discus throw. In this event, athletes attempt to throw the discus a maximum distance into a restricted landing area with a forehand sidearm movement. The discus throw has been a common track and field event since the original Olympic games of the ancient Greeks.
The discus is a heavy disc having a generally convex top surface, a generally convex bottom surface, and a smooth rim. The size and weight of the discus for various classes of athletes is set by track and field governing bodies. For example, the discus thrown by adult men is 22 centimeters (7.1 inches) in diameter and has a weight of 2 kilograms (4.4 pounds).
Although the size and weight of the discus is specified, the material of construction and the weight distribution is variable. A conventional discus is typically made of four parts: a top plate, a symmetrical bottom plate, a metal rim around the outer edges of the plates, and an interior weight. The interior weight typically has the shape of a spool with female threaded openings at the top and bottom to receive top and bottom screws that hold the assembly together. The top and bottom plates are typically made of plastic, hard rubber, wood, fiberglass, or carbon fiber. The top and bottom plates are sometimes coated with a thin gel. A common problem with conventional discuses is that the top and bottom plates are prone to cracking after repeated use.
Gill, U.S. Pat. No. 1,492,976, May 6, 1924, discloses a discus with a threaded metal rim. Roddy, U.S. Pat. No. 5,522,780, Jun. 4, 1996, discloses a discus with an asymmetrical weight distribution. Neither the Gill discus nor the Roddy discus has top plates with greater durability.
Accordingly, there is a demand for an improved discus. More particularly, there is a demand for a discus having top plates and bottom plates of greater durability.